agg_span_image_filter_rgb.h

这是VCF框架的代码

                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }

                    if(--y_count == 0) break;
                    y_hr  += image_subpixel_scale;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] >>= image_filter_shift;
                fg[1] >>= image_filter_shift;
                fg[2] >>= image_filter_shift;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //==========================================span_image_resample_rgb_affine
    template<class Source> 
    class span_image_resample_rgb_affine : 
    public span_image_resample_affine<Source>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef span_image_resample_affine<source_type> base_type;
        typedef typename base_type::interpolator_type interpolator_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::long_type long_type;
        enum base_scale_e
        {
            base_shift      = color_type::base_shift,
            base_mask       = color_type::base_mask,
            downscale_shift = image_filter_shift
        };

        //--------------------------------------------------------------------
        span_image_resample_rgb_affine() {}
        span_image_resample_rgb_affine(source_type& src, 
                                       interpolator_type& inter,
                                       const image_filter_lut& filter) :
            base_type(src, inter, filter) 
        {}


        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);

            long_type fg[3];

            int diameter     = base_type::filter().diameter();
            int filter_scale = diameter << image_subpixel_shift;
            int radius_x     = (diameter * base_type::m_rx) >> 1;
            int radius_y     = (diameter * base_type::m_ry) >> 1;
            int len_x_lr     = 
                (diameter * base_type::m_rx + image_subpixel_mask) >> 
                    image_subpixel_shift;

            const int16* weight_array = base_type::filter().weight_array();

            do
            {
                base_type::interpolator().coordinates(&x, &y);

                x += base_type::filter_dx_int() - radius_x;
                y += base_type::filter_dy_int() - radius_y;

                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                int y_lr = y >> image_subpixel_shift;
                int y_hr = ((image_subpixel_mask - (y & image_subpixel_mask)) * 
                                base_type::m_ry_inv) >> 
                                    image_subpixel_shift;
                int total_weight = 0;
                int x_lr = x >> image_subpixel_shift;
                int x_hr = ((image_subpixel_mask - (x & image_subpixel_mask)) * 
                                base_type::m_rx_inv) >> 
                                    image_subpixel_shift;

                int x_hr2 = x_hr;
                const value_type* fg_ptr = 
                    (const value_type*)base_type::source().span(x_lr, y_lr, len_x_lr);
                for(;;)
                {
                    int weight_y = weight_array[y_hr];
                    x_hr = x_hr2;
                    for(;;)
                    {
                        int weight = (weight_y * weight_array[x_hr] + 
                                     image_filter_scale / 2) >> 
                                     downscale_shift;

                        fg[0] += *fg_ptr++ * weight;
                        fg[1] += *fg_ptr++ * weight;
                        fg[2] += *fg_ptr   * weight;
                        total_weight += weight;
                        x_hr  += base_type::m_rx_inv;
                        if(x_hr >= filter_scale) break;
                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }
                    y_hr += base_type::m_ry_inv;
                    if(y_hr >= filter_scale) break;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] /= total_weight;
                fg[1] /= total_weight;
                fg[2] /= total_weight;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();
            } while(--len);
        }
    };



    //=================================================span_image_resample_rgb
    template<class Source, class Interpolator>
    class span_image_resample_rgb : 
    public span_image_resample<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_resample<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::long_type long_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask,
            downscale_shift = image_filter_shift
        };

        //--------------------------------------------------------------------
        span_image_resample_rgb() {}
        span_image_resample_rgb(source_type& src, 
                                interpolator_type& inter,
                                const image_filter_lut& filter) :
            base_type(src, inter, filter)
        {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            long_type fg[3];

            int diameter = base_type::filter().diameter();
            int filter_scale = diameter << image_subpixel_shift;

            const int16* weight_array = base_type::filter().weight_array();
            do
            {
                int rx;
                int ry;
                int rx_inv = image_subpixel_scale;
                int ry_inv = image_subpixel_scale;
                base_type::interpolator().coordinates(&x,  &y);
                base_type::interpolator().local_scale(&rx, &ry);

                rx = (rx * base_type::m_blur_x) >> image_subpixel_shift;
                ry = (ry * base_type::m_blur_y) >> image_subpixel_shift;

                if(rx < image_subpixel_scale)
                {
                    rx = image_subpixel_scale;
                }
                else
                {
                    if(rx > image_subpixel_scale * base_type::m_scale_limit) 
                    {
                        rx = image_subpixel_scale * base_type::m_scale_limit;
                    }
                    rx_inv = image_subpixel_scale * image_subpixel_scale / rx;
                }

                if(ry < image_subpixel_scale)
                {
                    ry = image_subpixel_scale;
                }
                else
                {
                    if(ry > image_subpixel_scale * base_type::m_scale_limit) 
                    {
                        ry = image_subpixel_scale * base_type::m_scale_limit;
                    }
                    ry_inv = image_subpixel_scale * image_subpixel_scale / ry;
                }

                int radius_x = (diameter * rx) >> 1;
                int radius_y = (diameter * ry) >> 1;
                int len_x_lr = 
                    (diameter * rx + image_subpixel_mask) >> 
                        image_subpixel_shift;

                x += base_type::filter_dx_int() - radius_x;
                y += base_type::filter_dy_int() - radius_y;

                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                int y_lr = y >> image_subpixel_shift;
                int y_hr = ((image_subpixel_mask - (y & image_subpixel_mask)) * 
                               ry_inv) >> 
                                   image_subpixel_shift;
                int total_weight = 0;
                int x_lr = x >> image_subpixel_shift;
                int x_hr = ((image_subpixel_mask - (x & image_subpixel_mask)) * 
                               rx_inv) >> 
                                   image_subpixel_shift;
                int x_hr2 = x_hr;
                const value_type* fg_ptr = 
                    (const value_type*)base_type::source().span(x_lr, y_lr, len_x_lr);

                for(;;)
                {
                    int weight_y = weight_array[y_hr];
                    x_hr = x_hr2;
                    for(;;)
                    {
                        int weight = (weight_y * weight_array[x_hr] + 
                                     image_filter_scale / 2) >> 
                                     downscale_shift;
                        fg[0] += *fg_ptr++ * weight;
                        fg[1] += *fg_ptr++ * weight;
                        fg[2] += *fg_ptr   * weight;
                        total_weight += weight;
                        x_hr  += rx_inv;
                        if(x_hr >= filter_scale) break;
                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }
                    y_hr += ry_inv;
                    if(y_hr >= filter_scale) break;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] /= total_weight;
                fg[1] /= total_weight;
                fg[2] /= total_weight;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();
            } while(--len);
        }
    };


}


#endif